1. Field of the Invention
This invention relates to a steam jet for fluid transfer applications, and more particularly to a steam jet that is cooled to prevent vaporization of the fluid being transferred as it is drawn into the steam jet.
2. Relevant Technology
There is an important need for moving contaminated fluids in nuclear reactors and other hazardous waste locations. One well known and acceptable mechanism for moving such fluid is what is commonly called a "steam jet." In a steam jet, steam passes through a venturi nozzle and discharges out one end. As the steam passes through the venturi nozzle, a vacuum is created which is communicated to the fluid that is to be displaced. The vacuum draws the fluid that is to be moved into the venturi nozzle.
Steam jets are particularly useful in the instances where the fluid is destructive to moving parts, corrosive, or is a hazardous/toxic material that presents a danger should it be sprayed or be dispersed. For example, steam jets are often used in applications where the fluid to be transferred may be a contaminated fluid in a nuclear reactor or may be a fluid filled with corrosive materials and/or hazardous components. In addition to the problems created by moving parts, traditional pumps that spray or otherwise disperse toxic materials are undesirable. An example of where steam jets are commonly used is in a chemical plant. Among the advantages of the steam jet are that it can be used to move very hazardous fluids, does not substantially dilute the hazardous fluid or contaminated material, and does not involve moving parts. An example of a particularly hazardous application is the ability of the steam jet to be utilized in nuclear reactors and nuclear processes facilities to move solutions of recovered fissile materials and radioactive waste. An additional and often key benefit of the steam jet that is specifically a result of the elimination of any moving parts is that a steam jet requires little maintenance. The reduced maintenance minimizes the potential contact with the hazardous or contaminated fluid.
Transporting fluids utilizing a steam jet, however, does have a serious drawback when the fluid that is to be transferred vaporizes at or below the temperature of steam. In these circumstances, the heat in the steam jet vaporizes the contaminated or hazardous fluid that is being drawn into the steam jet by the vacuum and creates what is called "vapor lock." Once a vapor lock occurs, a long delay is experienced until the heat in the steam jet dissipates sufficiently, and the steam jet is cool enough to attempt another transfer. A delay may cause an entire system to shut down. Any time the system is slowed down or shut down, it is costly as well as presenting a serious potential hazard. In addition, high temperatures are hard on equipment and can cause premature fatigue of the steam jet and pipes attached thereto.